Such processing stations are subsections of a production line in which CDs or other objects are produced section by section. Conveyance means and manipulator means are provided between the individual stations to transport the CD from a receptacle of one station to the receptacle of the next station. The conveyance means here can be realized as vacuum grippers or have, for instance, fork-shaped or annular supports on which the CD rests only at its edge area. The supports can also be provided with a conical internal wall, so that the CD makes contact only with its edge.
The object is housed by the receptacle and separated from the conveyance means, the receptacles for a CD being constructed such that they cooperate with the center hole of the CD. For this purpose, the receptacle has a peg-shaped, normally conical free end, which is adjoined by a flange-shaped shoulder extending perpendicular to the axis of rotation. The peg-shaped end serves as a guidance means, with the placement and centering of the CD being eased by the conicity. The axial orientation of the CD with respect to the processing station is defined by the shoulder. Depending on the type of processing being performed in the respective station, the receptacle can be constructed to be rotating or stationary. Particularly for a rotating receptacle, releasable fixation means or tensioning means are provided, in order to clamp the CD free of rotational play on top of the shoulder.
The processing stations are frequently constructed such that the CD is set down on the receptacle in a horizontal orientation. This has the advantage that the conveyance means can hold and transport the CD only based on its own weight, so that other clamping means are not required. The receptacle of a station in which the CD is processed while rotating is vertically oriented and can be rotated about a vertical axis.
Optical measuring methods are generally employed in examining a CD in order to examine the upper or lower side. First of all, it is necessary here that the CD have an exact and reproducible position in the receptacle. Second, it is necessary that the CD be rotated at least once about its axis of rotation, which runs perpendicular to its surface extension, in order to cover the entire surface with a linear scan.
Therefore, high demands are placed on the receptacle of a processing station with regard to exact rotary seating. To achieve a flawless measurement, it must be assured in particular that rotary driving is done without slippage. Because of these high demands, arranging the rotatable receptacle axially fixed in the processing station is a known measure.
This has the disadvantage that the conveyance means must perform complicated pivoting and lowering movements to first position the CD above the free end of the receptacle and subsequently to guide it down to the seat. Specifically, tumbling movements often occur then, which make a defined clamping and exact positioning impossible. There also exists the danger that the center hole is not moved over the conical free end of the receptacle and the CD falls past it and could thus cause a disruption of production. Moreover, the CD must then be lifted off the receptacle, which again requires the lowering motion of the conveyance means. The required pivoting motion of the conveyance means, on which several CDs are generally transported, is not easily performed, especially not in a short time, because of the relatively large mass involved.